Kill me if I overlooked an axle section... just trying to figure out the right way to go.

Is anyone running 35s? What are you 60, 70, 75 mph engine speeds? In a ford van: 1997 nv4500, 2007 nv271, 1990 12v with newer intercooler and stock h1c. VE turned up a bit by PO I assume since I can hit 22-23 psi. I have a he351cw to install sometime and plan to do the usual VE mods and maybe injectors down the line. Not going for madness just usable somewhat efficient power.

Current 3.54 with 265/75/1660, 169170, 197375, 2114

3.73 with 35s60, 161170, 188075, 2014

4.10 with 35s60, 177170, 206675, 2214

I don’t need to go 75 but definitely 72-73 to keep up with Florida traffic. Would the drop using 3.73 hurt me through 2,3,4 too much? Or lug too much on secondary roads?

I don’t tow much but when I do it’s my boat with trailer at about 5500-6k lbs. mostly around town and highway but we’ll be doing road trips (without towing for now) out west to find trails and use the lockers I put in. Obviously this is a full size van not a rock crawler but we’ll have fun. I feel with first being so low and add tcase low to that I shouldn’t be too worried about loosing low speed low end with the 3.73 just want to make sure it’s not a dog in 2nd and third. ...gear choices are for a sterling 10.5 and Dana 60 in front.

If you do a lot of driving/towing at 70-75 3:73's would be nicer to have, and won't feel doggy in the lower gears. A long trip at 70-80 mph would have you wishing for taller gears. Towing at 55-65 on hilly twisty roads may have you downshifting more vs 4:10's. Either should go wheeling fine with that t-case.